Theophilos was well-educated in the imperial household but upon his accession to the throne was met with the dual threat of the Abbasid Caliphate in Asia Minor and the Aghlabids in Sicily.

He won fleeting victories but the retaliation of Caliph al-Mu'tasim (r. 833–842) was devastating, as was most humiliating in the Sack of Amorion in 838, the ancestral home of Theophilos' Amorian dynasty.

The military defeats to the Arabs inspired a more intensely iconoclastic policy than what Theophilos inherited from his father Michael II and he persecuted many clerics for refusing to submit to the imperial will.

As with all iconoclast emperors, Theophilos was viewed critically by subsequent chroniclers however the historical record does witness to his reputation as a just ruler and keen constructor and administrator, partly thanks to a defence by his wife, later Empress regnant Theodora (r. 842–856).

[5] Unlike his father, Theophilos received an extensive education from John Hylilas, the grammarian, and was a great admirer of music and art.

In 830, Abbasid Caliph al-Ma'mun (r. 813–833) invaded Cappadocia in response to Theophilos' attack on Mopsuestia and Tarsos, capturing the city of Tyana.

Another defeat in Cappadocia forced Theophilos to sue for peace (a one-off tribute of 100,000 gold dinars and the return of 7,000 prisoners), which he secured the next year, after the death of al-Ma'mun in 833.

[10][11]During the respite from the war against the Abbasids, Theophilos arranged for the abduction of the Byzantine captives settled north of the Danube by Krum of Bulgaria.

On 21 July 838, at the Battle of Anzen in Dazimon, Theophilos personally led a Byzantine army of 25,000 to 40,000 men against the troops commanded by al-Afshin.

Although the Caliph was soon forced to retreat to Abbasid territory to suppress an insurgency, the defeat was a major blow to Theophilos' resources and prestige, and numerous Byzantine prisoners were executed.

The Sack of Amorion was the high point of Abbasid incursion past the Taurus Mountains, after which political strife within the Caliphate improved the Byzantine military situation.

[21] Despite major defeats at the hands of the Abbasids, the Byzantines consolidated and gained a degree of economic stability, and was no longer facing an existential threat.

Theophilos was a keen builder and administrator; through the construction of lavish palaces and exchange of precious goods and manuscripts, he intended to rival the court at Baghdad, which was itself seeing a revival of Hellenic thought.

In the tenth century, Liudprand of Cremona reported that Theophilos decorated the reception hall of the Magnaura with a throne and automata of lions and birds.

In 837, John the Grammarian returned from an embassy to Baghdad impressed by the architecture, and persuaded Theophilos to construct an "Abbasid"-style palace in Bryas near Chalcedon, which is now in ruins.

The only departure he made [from the Arab model] was that he built next to the bedchamber a church of our most holy lady, the Mother of God, and in the courtyard of the same palace a triconch church of great beauty and exceptional size, the middle part of which was dedicated to the archangel [Michael], while the lateral parts were dedicated to women martyrs.This passage has been interpreted as either a report of cultural receptivity and Theophilos' taste for Islamic motifs or as an iconodule fabrication to depict Theophanes and Patriarch John as Muslim-sympathisers.

In the palatine precinct of the Great Palace of Constantinople, Theophilos constructed buildings sheathed in marble with bronze and silver doors, fountains, a decorated armoury, mosaics, terraces, porticoes and gardens.

[27][28][29] When the Abbasids crushed the revolt of Babak Khorramdin in 838, many remaining Khurramite rebels fled to Byzantine territory and were accepted by Theophilos and placed under the command of Theophobos.

[30] The persistent warfare had caused a serious manpower shortage, which Theophilos attempted to remedy by resettling defectors from the Caliphate into Asia Minor, and issuing an edict requiring Roman widows to marry barbarian immigrants, which was reported in the Life of Athanasia of Aegina.

[33] However, the letter of Michael II to Carolingian Emperor Louis the Pious establishes that images that were not readily accessible and suspended high up in churches were permitted and commonplace.

[34][35] The majority of the clergy did not revolt against imperial policy, including Joannicius the Great, who was criticised for his compliance by Theodore the Stoudite, and Ignatios, later Patriarch of Constantinople.

Theophilos' enforcement of iconoclasm may have served as an opportunistic means of asserting imperial authority, rather than a purely theological endeavour, but there is no reason to doubt that he was sincere in his iconoclastic convictions.

The invasion led to a three-year war, in which Vlastimir was victorious;[42] Presian was heavily defeated, made no territorial gains, and lost many of his men.

As Theophilos' health was gradually failing in 842, he suspected that Theophobos would attempt a coup after his death, so he was invited to stay in the Great Palace of Constantinople.

[44][45] Theophilos was the last iconoclast emperor of the Byzantine Empire, and his strict insistence on the removal of images and banning of the production of icons as reported by later sources represents a return to the spirit of Constantine V's Council of Hieria of 754.

Theophilos' wife Theodora (r. 842–856) defended him, which mitigated the damnatio memoriae against him and his father Michael, nevertheless the later iconodule sources were highly critical of them.